Gas turbine engines, such as turbofan gas turbine engines, may be used to power various types of vehicles and systems, such as, for example, aircraft. Typically, these engines include turbine blades (or airfoils) that are impinged by high-energy compressed air that causes a turbine of the engine to rotate at a high speed. Consequently, the blades are subjected to high heat and stress loadings which, over time, may reduce their structural integrity.
Modern aircraft jet engines have employed internal cooling systems in the blades to maintain the blade temperatures within acceptable limits. Typically, the blades are air cooled using, for example, bleed air from a compressor section of the engine. The air may enter the blade near a blade root, and then flow through a cooling circuit formed in the blade. The cooling circuit typically consists of a series of connected cooling passages that form serpentine paths, which increase the cooling effectiveness by including an extended flow path along which the air may travel.
One exemplary cooling system is multi-walled and includes independent cooling circuits for surfaces of the blade. The cooling system may be configured to cool a pressure side wall, a suction side wall, and a tip wall, to thereby control specific heat load distributions thereon. The walls form intricate serpentine passages in an interior of the blade through which the cooling air flows. The serpentine passages may include pin fins, turbulators, turning vanes, and other structures therein. In some cases, a tip recess may be formed between the outer surfaces of the suction side wall, the pressure side wall, and the tip wall. The tip recess increases cooling capabilities of the tip wall to an extent and may also increase turbine engine efficiency by reducing an amount of leakage flow over the blade tip, which is driven by a pressure differential between the pressure side and suction side of the airfoil. However, as engine operating temperatures increase, improved cooling of the tip wall may be desired.
Accordingly, there is a desire for a blade having improved tip wall cooling over conventional blades. Additionally, it is desirable for the blade to be relatively simple and inexpensive to manufacture. Moreover, it is desirable for the improved blade to be capable of being retrofitted into existing systems.